The present invention is directed generally to printing with inks, and, more particularly, to enhancing a printed image on a print medium.
It is difficult to bond to a surface that contains oils or lubricants. The adhesive fails to bond because it has poor contact with the intended substrate.
Many types of printed media, including paper, have a lubricant or oil added to the surface of the media before or during the printing process. Types of printing that add oil or lubricant to the process include laser printers, oil-based ink press printing, and liquid electrophotographic (EP) toner printing. Examples of such materials include sizing agents applied to paper in the paper-making process and lubricants on EP fusers to prevent toner from adhering to paper.
A clear plastic film such at polyethylene terephthalate can be used to coat the print in order to protect it or to improve its image quality. A thin layer of adhesive is used to bond the film to the media. However, the oils or lubricant from the printing process prevent the film from adhering well to the media""s surface or image""s surface.
A prior solution using particles in an adhesive layer to improve adhesion between a clear film and a printable substrate was developed by Hewlett-Packard. Those particles were used for paper where excess water from Inkjet printing inhibited good adhesion. Hydrophilic silica was used to absorb some of the water. That was found to improve adhesion. However, that solution only addresses water in paper.
Accordingly, a need remains for adhering a thin transparent film to printed media that have oily or lubricated substrates.
One embodiment of the invention is directed to an adhesive composition that is clear, flexible, and is devoid of non-polar additives and comprises molecules that are polar and particles having a lipophilic surface. In one embodiment, the particles range from 7 nm to 3 xcexcm in diameter and the adhesive layer is between 0.1 and 5 xcexcm thick. The particles may be alkyl-converted fumed silica, porous polymer-coated surfaces, or styrene/divinyl benzene polymer. The preferred concentration of particles in the adhesive layer is between 1% and 70% by weight. The particles absorb non-polar oils or lubricants that prevent adhesion between printable media and the adhesive layer of the film.
The present disclosure is a general solution for oily or lubricated substrates or printed areas. Oily materials are used in inks, dry powder toners, liquid EP toners, and in printers and copiers. The present teachings allow the adhesive to bond well to print media surfaces.